Fluoxetine acts concomitantly on dorsal and ventral hippocampus to Trk-dependently modulate the extinction of fear memory

BACKGROUND

Hippocampus can be divided along its longitudinal axis into dorsal and ventral parts, which play different roles in modulating the behavioral responses to stress. However, it is not clear whether the hippocampal subregions could also differently modulate the effect of antidepressant drugs. Since fluoxetine (FLX) effect on extinction of aversive memory is well known to depend on hippocampal BDNF levels, we hypothesized that the hippocampal subregions might play different roles in fluoxetine efficacy in decreasing fear response.

METHOD

Wistar rats were fear-cued conditioned and treated chronically with FLX to subsequently investigate their extinction memory. BDNF levels were assessed separately in the dorsal (dHC) and ventral (vHC) hippocampus in animals chronically treated with FLX. An independent group received K252a (a functional Trk blocker) infusion into the dHC or vHC to assay its interaction with FLX treatment along the fear response. Next, BDNF was directly infused into either the dHC or vHC to the behavior be compared with those induced by chronic FLX treatment. Finally, FLX effect on c-Fos expression was evaluated also considering the dHC and vHC apart, along with subareas of amygdala and medial prefrontal cortex.

RESULTS

BDNF levels were increased in the vHC after acute FLX, and in the dHC after chronic FLX treatment. FLX effect on fear response was blocked by K252a administration into either dHC or vHC, after the extinction protocol. BDNF administration into the dHC increased fear response, however its administration into the vHC induced an opposite effect. Besides, a negative correlation between the fear response and c-Fos expression in the dHC CA3/CA1 and vHC CA1/DG was observed after chronic FLX treatment.

CONCLUSION

Both dHC and vHC are essential for the Trk-dependent effect of FLX on extinction memory, although a discrepancy in the fear response was observed with the infusion of BDNF into the dHC or vHC.

PPARγ receptors are involved in the effects of cannabidiol on orofacial dyskinesia and cognitive dysfunction induced by typical antipsychotic in mice

Tardive dyskinesia (TD) is a movement disorder that appears after chronic use of drugs that block dopaminergic receptors such as antipsychotics. Besides the motor symptoms, patients with TD also present cognitive deficits. Neuroinflammatory mechanisms could be involved in the development of these symptoms. A previous study showed that cannabidiol (CBD), the major non-psychotomimetic compound of Cannabis sativa plant, prevents orofacial dyskinesia induced by typical antipsychotics by activating peroxisome proliferator-activated receptors gamma (PPARγ). Here, we investigated if CBD would also reverse haloperidol-induced orofacial dyskinesia and associated cognitive deficits. We also verified if these effects depend on PPARγ receptor activation. Daily treatment with haloperidol (3 mg/kg, 21 days) increased the frequency of vacuous chewing movements (VCM) and decreased the discrimination index in the novel object recognition test in male Swiss mice. CBD (60 mg/kg/daily) administered in the last 7 days of haloperidol treatment attenuated both behavioral effects. Furthermore, haloperidol increased IL-1β and TNF-α levels in the striatum and hippocampus while CBD reverted these effects. The striatal and hippocampal levels of proinflammatory cytokines correlated with VCM frequency and discrimination index, respectively. Pretreatment with the PPARγ antagonist GW9662 (2 mg/kg/daily) blocked the behavioral effects of CBD. In conclusion, these results indicated that CBD could attenuate haloperidol-induced orofacial dyskinesia and improve non-motor symptoms associated with TD by activating PPARγ receptors.

Pitavastatin ameliorates autoimmune neuroinflammation by regulating the Treg/Th17 cell balance through inhibition of mevalonate metabolism

While Treg cells are responsible for self-tolerance and immune homeostasis, pathogenic autoreactive Th17 cells produce pro-inflammatory cytokines that lead to tissue damage associated with autoimmunity, as observed in multiple sclerosis. Therefore, the immunological balance between Th17 and Treg cells may represent a promising option for immune therapy. Statin drugs are used to treat dyslipidemia; however, besides their effects on preventing cardiovascular diseases, statins also have anti-inflammatory effects. Here, we investigated the role of pitavastatin on experimental autoimmune encephalomyelitis (EAE) and the differentiation of Treg and Th17 cells. EAE was induced by immunizing C57BL/6 mice with MOG35-55. EAE severity was determined by analyzing the clinical score and inflammatory parameters in the spinal cord. Naive CD4 T cells were cultured under Treg and Th17-skewing conditions in vitro in the presence of pitavastatin. We found that pitavastatin decreased EAE development, which was accompanied by a reduction of all parameters investigated. Pitavastatin also reduced the expression of IBA1 and pSTAT3 (Y705 and S727) in the spinal cords of EAE mice. Interestingly, the reduction of Th17 cell frequency in the draining lymph nodes of EAE mice treated with pitavastatin was followed by an increase of Treg cells. Indeed, pitavastatin directly affects T cell differentiation in vitro by decreasing Th17 and increasing Treg cell differentiation. Mechanistically, pitavastatin effects are dependent on mevalonate synthesis. Thus, our data show the potential anti-inflammatory effect of pitavastatin on the pathogenesis of the experimental neuroinflammation by modulating the Th17/Treg axis.

Cannabidiol attenuates behavioral changes in a rodent model of schizophrenia through 5-HT1A, but not CB1 and CB2 receptors

Preclinical and clinical data indicate that cannabidiol (CBD), a non-psychotomimetic compound from the Cannabis sativa plant, can induce antipsychotic-like effects. In an animal model of schizophrenia based on the antagonism of NMDA receptors, the behavioral and molecular changes induced by repeated treatment with the NMDA receptor antagonist MK-801 were prevented when CBD was co-administered with MK-801. It is unknown, however, if CBD would reverse these changes once they have been established. Thus, in the present study we used male C57BL/6J mice, 6 weeks old, to evaluate whether daily CBD injection for seven days, starting after the end of the repeated treatment with MK-801 for 14 days, would reverse MK-801-induced deficits in the social interaction (SI) and novel object recognition (NOR) tests, which have been used to investigate the negative and cognitive symptoms of schizophrenia, respectively. We also assessed whether CBD effects would be blocked by pretreatment with AM251, a CB1 receptor antagonist, AM630, a CB2 receptor antagonist, or WAY100635, a 5-HT1A receptor antagonist. CBD and the second-generation antipsychotic clozapine, used as a positive control, attenuated the impairments in the SI and NOR tests induced by repeated administered MK-801. CBD effects were blocked by WAY100635, but not by AM251 or AM630. These data suggest that CBD induces antipsychotic-like effects by activating 5-HT1A receptors and indicate that this compound could be an interesting alternative for the treatment of negative and cognitive symptoms of schizophrenia.